1. Field of the Invention
The present general inventive concept relates to a reflection unit having a mirror array and a projection display system employing the same, and more particularly, to a reflection unit and a projection display system in which a mirror array is provided to maximize a reflection region of a beam reflected from the mirror array toward a screen, thereby achieving a reduced depth dimension for the projection display system.
2. Description of the Related Art
In a projection display system, a display element controls light exiting from a lamp light source to form a color image having a plurality of pixels, and the color image is magnified and projected to a screen. Recently, demand has increased for projection display systems having a reduced depth dimension (i.e., reduced thickness) and a large screen. Accordingly, various projection display systems have been developed.
In order to reduce the depth dimension of the projection display system, a depth dimension of a square pendulum of a beam bundle from a projection optical system should be reduced. However, if the projection optical system is disposed at a center of the screen, reduction of the depth dimension of the square pendulum of the beam bundle from the projection optical system is limited. Accordingly, in order to reduce the depth dimension of the square pendulum, the projection optical system is disposed at an angle at a bottom side of the screen.
In addition, various other technologies are being developed in an attempt to increase the size of the color image projected on the screen while reducing the depth dimension of the projection display system. However, there is a difficulty in reducing the depth dimension, since the screen is large and a. That is, there is a trend in which the entire projection optical system is increased in size in order to increase the size of the screen. However, there is a technological difficulty in reducing the size of the entire projection optical system while reducing the depth dimension of the projection display system.
Further, the projection optical system is disposed at an angle at the bottom side of the screen, and a beam exiting the projection optical system is reflected by a reflection mirror to propagate toward the screen. Since the projection display system has a compact depth, the beam exiting the projection optical system should have a large spreading angle.
A projection display system is disclosed in U.S. Patent Application Publication No. 2003/0072077. Referring to FIG. 1, the projection display system includes a cabinet 12 and a screen 14. The cabinet 12 includes an image source 16 for forming a color image, a first reflection mirror 18 for reflecting images 34 and 34′ from the image source 16, and a second reflection mirror 20 for reflecting the image (i.e., the images 34 and 34′) received from the reflection mirror 18 toward the screen 14.
The screen 14 includes a reflection element 30 arranged in a vertical direction. The reflection element 30 has a reflection surface 32 disposed to slant downward and toward an inside of the cabinet 12.
An image path in the projection display system of FIG. 1 is now described.
An image produced by the image source 16 is primarily reflected from the first reflection mirror 18 to be incident on the second reflection mirror 20. The image is then reflected from the second reflection mirror 20 to the reflection element 30 of the screen 14. The reflection element 30 includes the reflection surface 32 and a rear surface 33. The reflection element 30 then reflects a first part of the image back to the second reflection mirror 20, and transmits a second part of the image through the reflection element 30 of the screen 14.
The projection display system of FIG. 1 has a disadvantage in that a contrast deteriorates as a result of the image being reflected twice from the second reflection surface 20 to be incident twice on the screen 14.
Further, since the second reflection mirror 20 is a plane mirror, an effective image region (A) on which the image is incident on the screen 14 is small. Since the effective image region (A) is different from a region (B) at which the image is primarily reflected on the second reflection mirror 20, there is a disadvantage in that an effective screen size is reduced compared to an actual screen size.